Metal particulate production

ABSTRACT

Method to produce metal particulate by contacting at least a portion of a metal coated substrate with a liquid, which is substantially nonreactive with the metal, and subjecting at least a portion of the metal coating to sufficient ultrasonic vibration to release at least a portion of the coating and form metal particulate.

United States Patent 1 91 1111 3,839,012

Roberts Oct. 1, 1974 {54] METAL PARTICULATE PRODUCTION 2,980,345 4/l96l Kccccioglu ct all. 24l/l 2,997,245 8/1961 N'l t'l. t 24| I [75] Inventor: Charles R0berts, Mlch- 3,284,010 11/1966 241/1 x [73] Assignee: The Dow Chemical Company,

Midland, Mich. Primary Examiner-L. Dewayne Rutledge Assistant ExaminerArthur J. Steiner [22] led: 1973 Attorney, Agent, or Firm-William M. Yates; Robert [21] Appl. No.: 409,355 W. Selby; Lloy S. Jowarovitz 52 us. c1 75/.5 R, 148/129, 241/1 [57] ABSTRACT [51] Int. Cl. B02c 19/18 MethOd to P oduce metal particulate by contacting at [58] Field of Search 75/.5; 264/9; 148/129; least a por ion of a metal coated substrate with a liq- 241/1 uid, which is substantially nonreactive with the metal, and subjecting at least a portion of the metal coating [56] References Cited to sufficient ultrasonic vibration to release at least a UNITED STATES PATENTS portion of the coating and form metal particulate.

2,722,498 11/1955 Morrell et al 241/1 X 17 Claims, N0 Drawings METAL PARTICULATE PRODUCTION BACKGROUND OF THE INVENTION This invention pertains to the production of metal particulate and more in particular to the production of metal particulate by the ultrasonic removal of a metal coating from a substrate.

Metal powders, chips, shot and the like have long been produced by well known procedures. It is desired to provide a method capable of rapidly and readily forming metallic particulate at low temperatures. It is further desired to provide a metallic particulate in the form of a platelet which has reflective properties on at least one surface of the particulate.

SUMMARY OF THE INVENTION It has been found that metal particulate can be formed by contacting at least a portion of a metal coated substrate with a liquid, which is substantially nonreactive with the metal, and then subjecting the liquid and at least a portion of the metal coating to sufficient ultrasonic vibration to release at least a portion of the subject coating. The metal particulate so formed is suitable for, for example, an additive to molded plastics or a coating composition such as a paint.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic or inorganic substrate such as a film, sheet, plate and the like is preferably at least partially coated on at least one surface with a metal which can be deposited onto the substrate by a vapor (including vacuum), electroless or sputter deposition method. Exemplary of such metals are Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, In, Cd, Ag, Pd, Rh, Ru, Mo, Nb, Zr, Y, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, TI and Pb. The metal is preferably Mg, Al, Cu, Ag, or Au. Preferably a layer of aluminum is deposited on the substrate surface. As used herein the term metal includes the stipulated base metal and alloys thereof containing greater than 50 weight percent of the base metal.

The specific configuration of the substrate is not critical; however, it is preferred that the substrate be a solid film, sheet, plate and the like. Although inorganic materials, including metals, are satisfactory materials to employ as the substrate, it is preferred that the substrate be an organic composition. It is desirable to apply a release coating of, for example, a silicone resin type to the substrate prior to application of the metal coating. The metal coating is then applied directly to the release layer to form a composite having the release layer interposed between the metal coating and the substrate. By means of such release layer the metal is more easily removed from the substrate which can thereafter be reused for deposition of a metal layer thereon.

The metal coated substrate is at least partially and preferably entirely contacted with a liquid which is substantially and preferably entirely nonreactive with the metal coating. For example, the coated substrate can be totally immersed in an inert liquid bath and withdrawn therefrom after at least a portion, and preferably substantially all of the metal coating has been removed from the substrate. Such immersion can be carried out in either a batch-wise or continuous process. In a preferred embodiment the liquid is a solvent for only the release layer.

During immersion of the coated substrate in the liquid, the liquid and substrate are subjected to sufficient ultrasonic vibration to remove at least a portion and preferably substantially all of the metal coating. Metal particulates of various configurations are obtained by means of a described process. For example, the particulate can be acicular and preferably platelet shaped. A multiplicity of platelets with at least one reflective or lustrous surface is highly desirable when such platelets are employed as an additive to a coating composition. A highly reflective or specular surface can be obtained by, for example, application of such metallized coating composition to a surface of a transparent body such as a plate glass sheet.

The aluminum particulate generally remains within the liquid after removal of the substrate therefrom. The particulate can be removed from the liquid by, for example, well known centrifugal, filtering or sedimentation means. The particulate can then be dried and stored for later use, although for some purposes it is satisfactory to use the original liquid-metal particulate mixture without separation of the particulate from such mixture. The substrate can be reused to provide a surface for the deposition of a second or subsequent metallic coat thereon.

The following examples further illustrate the invention.

EXAMPLE l Mylar plastic film coated with a silicone resin type release agent, a lacquer overcoating and a vapor deposited coating of aluminum on the lacquer surface was immersed in a container of toluene. An ultrasonic probe was placed in the toluene and actuated for a period of about one minute. The ultrasonic vibration was provided by commercially available 150 watt equipment generating 25 kilohertzat full power by means of a magneto-strictive transducer. After about one minute of exposure to the ultrasonic-toluene environment at room temperature a majority of the aluminum coating on the Mylar plastic film had been removed and was observed as a multiplicity of finely divided, platelet type particles sparkling within the toluene.

COMPARATIVE EXAMPLE In a manner substantially as described in Example 1 an aluminum coated Mylar plastic film was immersed in toluene for about 30 minutes without exposure to ultrasonic energy. No visible aluminum particulate was formed during this time period.

EXAMPLE 2 Reflective aluminum particulates with slightly curled edges were produced in a manner similar to that described in Example 1, except that the aluminum coated Mylar plastic film was immersed for about 5 minutes in methanol at room temperature. About per cent of the aluminum coating was removed from the substrate and formed shiny aluminum platelets.

What is claimed is:

l. A method of forming metal particulate comprising contacting at least a portion of a metal coated substrate with a liquid substantially nonreactive with the metal and subjecting the liquid and at least a portion of the metal coating to sufficient ultrasonic vibration to release at least a portion of the subjected coating and form metal particulates.

2. The method of claim 1 wherein the metal coated substrate has a release layer interposed between the coating and the substrate.

3. The method of claim 2 wherein the liquid is a solvent for the release layer.

4. The method of claim 3 wherein the release layer is a silicone resin.

5. The method of claim 3 wherein the metal is aluminum.

6. The method of claim 2 wherein the metal is selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, ln, Cd, Ag, Pd, Rh, Ru, Mo, Nb, Zr, Y, La, Hf, Ta, W, Re, Os, lr, Pt, Au, Tl, and Pb.

7. The method of claim 6 wherein the particulates are platelets.

8. The method of claim 7 wherein the metal coating is vapor deposited.

9. The method of claim 2 wherein the metal is selected from the group consisting of Mg, Al, Cu, Ag and Au.

10. The method of claim 2 wherein the metal is aluminum.

11. The method of claim 10 wherein the particulates are platelets.

12. The method of claim 11 wherein the aluminum platelets are suitable as an additive to a coating composition.

13. The method of claim 11 wherein the aluminum coating is vapor deposited.

14. The method of claim 1 wherein the metal coated substrate is at least partially immersed in the liquid.

15. The method of claim 1 wherein the metal coated substrate is a film.

16. The method of claim 1 wherein the liquid is nonreactive with the substrate and the metal.

17. The method of claim 1 including the additional step of removing the metal particulates from the liquid. l 

1. A METHOD OF FORMING METAL PARTICULATE COMPRISING CONTACTING AT LEAST A PORTION OF A METAL COATED SUBSTRATED WITH A LIQUID SUBSTANTIALLY NONREACTIVE WITH THE METAL AND SUBJECTING THE LIQUID AND AT LEAST A PORTION OF THE METAL COATING TO SUFFICIENT ULTRASONIC VIBRATION TO RELEASE AT LEAST A PORTION OF THE SUBJECTED COATING AND FORM METAL PARTICULATES.
 2. The method of claim 1 wherein the metal coated substrate has a release layer interposed between the coating and the substrate.
 3. The method of claim 2 wherein the liquid is a solvent for the release layer.
 4. The method of claim 3 wherein the release layer is a silicone resin.
 5. The method of claim 3 wherein the metal is aluminum.
 6. The method of claim 2 wherein the metal is selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, In, Cd, Ag, Pd, Rh, Ru, Mo, Nb, Zr, Y, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl, and Pb.
 7. The method of claim 6 wherein the particulates are platelets.
 8. The method of claim 7 wherein the metal coating is vapor deposited.
 9. The method of claim 2 wherein the metal is selected from the group consisting of Mg, Al, Cu, Ag and Au.
 10. The method of claim 2 wherein the metal is aluminum.
 11. The method of claim 10 wherein the particulates are platelets.
 12. The method of claim 11 wherein the aluminum platelets are suitable as an additive to a coating composition.
 13. The method of claim 11 wherein the aluminum coating is vapor deposited.
 14. The method of claim 1 wherein the metal coated substrate is at least partially immersed in the liquid.
 15. The method of claim 1 wherein the metal coated substrate is a film.
 16. The method of claim 1 wherein the liquid is nonreactive with the substrate and the metal.
 17. The method of claim 1 including the additional step of removing the metal particulates from the liquid. 